In U.S. Pat. Nos. 7,138,443; 8,212,073; 8,703,853 and US application No. 2006/0175587 and PCT/US12/000247, all of which are incorporated herein by reference, ethyleneamine polyphosphates (EAPPA) are made from polyphosphoric acid (PPA) that was made by an ion exchange process because sodium polyphosphate has high molecular weight. In U.S. Pat. No. 7,138,443, it is specifically stated that it is preferred to make ethyleneamine polyphosphates with PPA from ion exchange process and not to use commercial polyphosphoric acid, which has much lower molecular weight. In US application No. 2006/0175587 (PCT/US2003/017268), with an international filing date of 3 Jun. 2003, Maya Kasowski shows that flame retardant diethylenetriamine polyphosphate (DETAPPA) compositions made with ion exchange have much better thermal stability that with commercial polyphosphoric acid, DETA, and water. It was stated explicitly that diethylenetriamine polyphosphate (DETAPPA) made with commercial PPA, DETA, and water could not be used above 250° C. in an extruder and thus is not suitable for mixing with nylon 66. It was also shown that DETAPPA with a pH of 5.3 ran poorly when mixed into polypropylene but DETAPPA with a pH of about 3.2 ran well with PP.
Syrup (approximately 60% EAPPA, 40% water) has a density of about 1.44 and separates to bottom of reaction vessel. EAPPA make with commercial PPA in these earlier references was not found to result in syrup when dissolved in water. One of the claims in U.S. Pat. No. 8,703,853 is that dehydration of the flame retardant syrup results in ethyleneamine polyphosphate with the property that when 3 g are dissolved in 20 ml water, at least 1.5 ml of syrup forms with a clear interface with the non-viscous phase. The formation of syrup was presented to be indicative of high molecular weight EAPPA, high thermal stability, and the best performance in an extruder. The ion exchange process used sodium polyphosphate with average chain length at least 11 suggesting such a molecular weight. Formation of syrup was associated with the highest quality EAPPA in terms of thermal stability, which will be shown to be inadequate criteria.
Such behavior does not occur when commercial polyphosphoric acid is used according to U.S. Pat. No. 8,212,073. In U.S. Pat. No. 8,212,073, it is specifically stated that “Syrup was only formed when an ethyleneamine such as EDA, DETA, TETA, and PEHA were reacted with ion exchange prepared polyphosphoric acid. The syrup did not form when commercial polyphosphoric acid was reacted with an ethyleneamine. Syrup also does not reform. For example, dry the syrup to form a flame retardant composition. Re-dissolve the flame retardant composition in water and the syrup phase does not separate.” In U.S. Pat. No. 8,703,853, it is stated that ion exchange is the preferred process to make ethyleneamine polyphosphates. However, the EAPPA from the ion exchange process suffered a significant reduction in pH during drying of the syrup. Syrup with pH 5 was found to be reduced to a pH of about 3.5 by drying. IX process has substantial waste stream.